As Alexander Haig continues in his diplomatic shuttle between London and Buenos Aires, military positions are hardening and wartime preparations accelerate.
Argentina and Britain are working swiftly to enhance the relative advantages that they hold, the former on land and in the air and the latter at sea. They know, as do US officials, that the nature of any engagement could quickly shape its outcome.
If Argentina challenges the British blockade, says a top Pentagon official, there is ''very, very little possibility that there can be any other outcome than that the Royal Navy will make very short work of the Argentine Navy.'' On the other hand, says this senior strategist, an attempt by the British to retake the islands by force ''could end up being a very bloody engagement because the Argentines have had time to put a great deal of equipment and supplies and men ashore.''
Meanwhile, the military involvement now has spread to other countries. The US apparently is supplying Britain with intelligence information, communication services, weather information, and a stockpile of fuel at the convoy's Ascension Island midway point.
The Soviet Union likewise is reportedly providing Argentina with intelligence information from its long-range patrol aircraft, satellites, and oceangoing vessels. Bolivia, Peru, and Equador are offering military assistance to their Latin American neighbor.
Overall, says Secretary Haig, the situation is ''dangerous and increasingly so.''
The British fleet is approaching the halfway point in its 8,000-mile journey to the South Atlantic. But the most powerful part of its naval power already is in place.
These are the four modern nuclear-powered attack submarines. They can stay beneath the surface for weeks at a time and have advanced wire-guided Tigerfish torpedoes that allow them to find and hit surface ships up to 30 miles away. If they surface, the British subs can hit targets 60 miles away with their Harpoon surface-to-surface missiles.
The Argentine Navy includes some antisubmarine helicopters, but they are based aboard that country's lone and aged aircraft carrier, a likely immediate target in a naval encounter. This ship also carries 18 American-made A-4 Skyhawk light attack aircraft, combat-proven in Vietnam but first introduced in the 1950 s.
Argentina has a total of 68 Skyhawks, 9 British-built Canberra bombers (also relatively old), and a squadron of about 20 modern Mirage fighters. Argentine ships are equipped with radar and antiaircraft weapons newer than the ships themselves.
Recognizing the threat presented by the British subs, Argentine naval commanders have ordered their ships to port and reportedly laid mines nearby.
Acknowledging the relative Argentine air superiority (Argentine has 223 combat aircraft, including planes with greater combat radius), the British Defense Ministry says it is doubling the number of Harrier jumpjets in the Royal Fleet to about 40.
Argentina, meanwhile, is sending its Mirages and other aircraft to the airfield at Port Stanley in the Falklands (which Argentina calls the Malvinas). It also is lengthening the relatively short runway there, beefing up antiaircraft batteries, and increasing the number of troops on the island to nearly 10,000. American-built C-130 transport aircraft will continue to play a key role for the Argentinians.
''You can put up a naval blockade, but that's not going to keep the C-130s out,'' says a Pentagon spokesman.
For this reason, say US military experts, the airfield at Port Stanley is likely to be an early British target if combat cannot be avoided. ''If I were the Brits, I would think getting that airfield out of operation would be my No. 1 priority,'' said retired Adm. Stansfield Turner, former director of US Central Intelligence Agency. Bomb-laden Harriers or perhaps demolition teams could be used for this purpose, he suggests.
British marines and commandos aboard the Royal Fleet are vastly outnumbered by the Argentine force now in place on the disputed island. ''But you've also got to evaluate the quality of the fighting man and how they're going to stack up against each other,'' says a US naval officer, suggesting that the British have the edge.
If there is to be any ground battle, US analysts anticipate that it could come first at South Georgia, an island 800 miles east of the Falklands also taken by the Argentinians. This could be a highly symbolic victory for the British and provide them with an important staging area in the region.
''It may be one way to ratchet up the pressure without taking a high risk,'' says a US intelligence expert.